What is the chance that an earthquake of magnitude 6.7 or greater will occur before the year 2030 in the San Francisco Bay Area? The U.S. Geological Survey estimated the chance to be 0.7 ± 0.1 (USGS, 1999). In this paper, we try to interpret such probabilities. Making sense of earthquake forecasts is surprisingly difficult. In part, this is because the forecasts are based on a complicated mixtu...
